Two Ruellias

-- What’s the difference; what does it matter?

Published June 6, 2026, in the McAllen Monitor

Violet Wild Petunia (Ruellia nudiflora). (Photo by Anita Westervelt)

Story and photos by Anita Westervelt, Texas Master Naturalist

Purple ruffled petals and deeper purple nectar guides provide the powerful attraction of Mexican petunia (Ruellia simplex) and violet wild petunia (Ruellia nudiflora) to anthophiles and insects alike.

Botanical enthusiasts love the sturdy, shrubby, tall growth and year-round blooms that Mexican petunia provide, while bees, butterflies and hummingbirds make use of a good nectar source. But one specific caution detracts from its local value. Mexican petunia is invasive in Texas.

Mexican petunia (Ruellia simplex). (Photo by Anita Westervelt)

Mexican petunia is especially aggressive because it spreads covertly underground via runners, making it capable of forming dense thickets, even creating new shoots from those lateral roots. In addition, broken off stem fragments can also easily take root in moist soil and establish new plants.

Native violet wild petunia, on the other hand, is more well-behaved – sort of. It is native to the southern United States and south through Mexico and Central America. Mexican petunia is native to a broader region which spans Mexico, the Caribbean, West Indies and Central and South America.

 Native Violet Wild Petunia (Ruellia nudiflora). (Photo by Anita Westervelt)

Both species are completely maintenance free and thrive in shade or full sun. Both are heavy seed producers and disperse seeds explosively, exhibiting a botanical term called dehiscent, whereby seed capsules, when ripe, forcefully shoot seeds – sometimes as far as 10 feet from the parent plant. One source mentioned seeds of the native plant could have a 30-foot trajectory.

Flowers of both species may appear identical, but growth habit and leaf structure differences are noticeable even at a quick glance. The nonnative, woody-based Mexican petunia grows to about three or four feet tall. The shrub is thick with long, narrow, linear dark green leaves to 12 inches in length. Flowers bloom along the stems from the upper angle where the leaf grows from the stalk. Bloom color can range from deep purple to lavender, bluish-purple and violet. Some varieties produce pale pink or white blooms.

Pink-blooming variety of Mexican Petunia. (Photo by Anita Westervelt)

A dense mat of errant Mexican petunia mowed over repeatedly in vain. (Photo by Anita Westervelt)

Both the nonnative and native species are perennial, however native violet wild petunia more often than not dies back during a harsh winter and re-emerges in spring, blooming profusely spring through fall. The shorter, native plants are 12 to 18 inches tall. Flowers are irregularly branched in loose, leafy clusters at branch ends. The leaves are grayish green to dark green and oblong with obvious venation and toothed edges.

The native violet wild petunia is beneficial to a native landscape and local wildlife. It is a primary nectar source for pollinators, including bees, hummingbirds and butterflies. It is a key larval host for common buckeye, white peacock, malachite and several crescent butterflies.

Even though Ruella nudiflora is a pretty and useful native plant and an asset to butterfly and pollinator gardens, because of its proclivity for energetic seed dispersal, it may become annoying if not managed.

Manually digging out the entire root system is one tactic of management. Lady Bird Johnson Wildflower Center has a simple management plan, which is to “cut back or mow established patches before flowers mature to prevent the explosive seed pods from launching seeds across your yard.”

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